Fiber reinforced thermoplastic structural member

ABSTRACT

In the manufacture of a structural member comprising a thermoplastic composite core with an exterior reinforcing layer, the core member is initially extruded in the shape of a profile. The profile is then contacted with reinforcing fiber and resin to form the exterior reinforcing layer. The exterior thermosetting layer is cured to form a reinforcing layer. The structural member is preferably manufactured using a pultrusion method in which a tractor device is used to provide linear movement of the profile from the extrusion head to the exterior coating operation. The fiber-reinforced thermoset is coated on the entirety of the exterior of the profile or is applied only on a portion of the profile requiring reinforcement in a defined load-bearing direction. The preferred thermoplastic core comprises a polymer-fiber composite material. Such a structural member has significantly improved Young&#39;s modulus providing strength for applications such as telephone poles, electric poles, electric lighting poles, boat mast or keel applications, lumber replacements, structural members used in window and door manufacture, etc.

FIELD OF THE INVENTION

The invention relates to shaped (non-circular) fiber-reinforcedstructural members. More particularly, the invention relates tofiber-reinforced structural members having an exterior fiber-reinforcedthermoset layer formed on a thermoplastic profile. Such reinforcedprofiles have a variety of useful cross-sectional shapes havingacceptable mechanical strength for high structural loading. Theinvention also relates to a pultrusion method of forming such astructural member involving an extrusion die for the formation of athermoplastic profile comprising a thermoplastic composite. The processfurther involves forming an uncured layer of fiber and thermosettingresin on the profile exterior which can be cured to form the reinforcedstructural member. The useful shapes of the profile can be complex forspecific application in window/door manufacture, automotive, aviation,I. beam and C-channel, and other applications as structural members.Further, the invention also relates to structural units using thefiber-reinforced structural member for increased strength.

BACKGROUND OF THE INVENTION

A great deal of attention has been directed to the fabrication ormanufacture of structural members that can withstand substantialstructural loads and varying temperatures arising in the naturalenvironment. In certain arid desert areas, average daily temperaturescan reach 100° F. or more. Most common structural members comprise asupport structure using either metallic structures manufactured fromaluminum, steel, stainless steel metallic fiber or other high strengthmetallic material. Further, large structural wooden members have beenused in utility poles, bridge components, housing structures and othersimilar units. Such wooden and metallic structural members have had somesubstantial success.

Increasing attention has also been given to the manufacture ofstructural members from thermosetting and thermoplastic materials.Processing these materials offers improved manufacturing propertiesbecause of the ease of processing thermosetting and thermoplastic resinsand combining those materials with reinforcing fibers.

Karino et al., U.S. Pat. No. 4,515,737 teach a process for producing acomposite circular composite pipe. In the process, a thermoplastic resinpipe is formed using an extruder. The surface of the pipe is coveredwith a uniform layer comprising continuous fibrous reinforcing materialimpregnated with a thermosetting resin in its axial direction by a drawmolding method, helically winding a continuous fibrous reinforcingmaterial impregnated or not impregnated with a thermosetting resinuniformly on the initial resin fibrous reinforced layer. The Karino etal. material has a polyvinyl chloride pipe center and a first and secondfibrous reinforcing layer. This process, using a wrapped layer, cannotbe used for complex profile shapes.

Tanaka et al., U.S. Pat. No. 4,740,405 teach an extruded profile orframe member comprising a thermoplastic resin having reinforcing wiresthroughout the frame member joined using a thermosetting resin. Thefibers are typically dispersed within the profile material.

Balazek et al., U.S. Pat. No. 4,938,823 teach a pultrusion/extrusionmethod in which continuous transit or longitudinal fiber or roving iscoated with a thermosetting resin. The fibers are then combined with oneor more fibrous reinforcing mats and pass through a second die to curethe thermosetting resin. This process forms a first profile. The surfaceof the substantially cured thermoset is then deformed and athermoplastic resin is then applied to the deformed surface. Thedeformity in the thermosetting surface provides increased adhesionbetween the thermoset core and the thermoplastic exterior.

Hirao et al., U.S. Pat. No. 5,030,408 teach a method of forming a moldedresin article combining both thermoplastic and thermosetting resins in akneader extruder to form the article. The structures manufactured byagglomerating thermoplastic materials having a particle diameter of0.05-0.5 μm with particles of 10-1000 μm diameter prior to kneading,then introducing the thermoplastic material into the kneader.

Strachan, U.S. Pat. No. 5,120,380 teaches a method of forming extrudedprofiles. In the process, cloth, preferably woven fiberglass isdelivered by supply rolls and guided over the external profiled surfaceof a forming duct. The cloth is maintained in a shape by an air streamprovided by a venturi blower. The air stream blows towards the die andat least partially diffuses through the cloth prior to the resin curingdie. The air shaped cloth runs into a curing die where it is impregnatedwith a thermosetting resin. The thermosetting resin is cured into anextruded profile which is then withdrawn from the curing station using apultrusion tractor device. The prior art shows a variety ofthermoplastic/thermosetting composite materials that can be used asstructural members. No one structure or method appears to be superior informing structural members that can resist high structural loads in thevarying temperatures found in the natural environment. Substantial needexists for improving the heat distortion temperature of compositestructures. cl BRIEF DISCUSSION OF THE INVENTION

The structural member of the invention comprises a core thermoplasticfiber reinforced non-circular profile having at least a coveringcomprising a fiber reinforced thermosetting layer. This structure can bemanually laid up or made in a continuous pultrusion process. We havealso found that the very high strength structural members can bemanufactured by extruding a core structure comprising a fiber reinforcedthermoplastic core, carefully calibrating the exterior of the core toform a core shape, covering the core with a thermoset resin fiberreinforced layer, shaping the exterior layer to calibrate the exteriorshape and curing the exterior layer to form the final structural member.Such a process can be incorporated in a pultrusion method in which atractor device is used to provide movement of the member through theprocess. A tractor device can contact the device after the fiberreinforced thermoset layer is calibrated, cured and cooled into a finalstructural member. An optional tractor device can be installed in aplace such that they can directly contact the thermoplastic extrudateafter calibration and cooling, but just prior to coating with the fiberreinforced thermoset. In the process, the cooled, calibrated,thermoplastic composite acts as a forming mandrel for the thermosettinglayer. The thermoplastic fiber reinforced composite layer hassubstantially improved structural properties when compared tonon-reinforced thermoplastics. The fiber reinforced thermoplastic, whenadhered to the fiber reinforced thermoset in a structural member,cooperates to result in substantially improved mechanical properties andin particular, substantially improved heat distortion temperatures whenused in a structural member under substantial load at high temperatures.

We have found that the fiber reinforced thermosetting layer has asubstantially higher heat distortion temperature than non-fiberreinforced thermoplastics. In particular, a fiber reinforced polyvinylchloride layer has a sufficiently higher heat distortion temperaturethan the non-reinforced thermoplastic such that an extruded fiberreinforced polyvinyl chloride can act as a moving mandrel in a manual orcontinuous process for making the structural members of the invention.Substantially complex shapes having a substantial quantity of boththermoplastic core material and reinforced thermosetting material can beused in forming the structural member of the invention (even in thepresence of substantial amounts of force in shaping the structure usinga die or vacuum forming device) without any substantial change to theshape, wall thickness or structural integrity of the fiber reinforcedthermoplastic core structure.

The structural components of the invention can be used in the form ofI-beams, C-channel, reinforced panels, rails, jambs, stiles, sills,tracks, stop and sash. The structural components of the invention can beheated and fused to form high strength welded joints in window and doorassembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representation of a continuous process of the inventionproducing the reinforced members.

FIG. 2 is a cross-sectional view of a complex shape structural member ofthe invention. Such a complex shape can be manufactured using theprocess of the invention.

DETAILED DISCUSSION OF THE INVENTION

The composite structural member of the invention comprises athermoplastic composite linear extruded core. This extruded core membercan comprise a thermoplastic polymer composite composition manufacturedby intimately combining a thermoplastic polymer and a fiber material.Preferably, the polymer comprises a polyvinyl chloride polymer and thefiber comprises a cellulosic fiber. The exterior reinforcing layer thatcan cover a portion or all of the composite structural member and cancomprise fiber and a thermosetting resin. The fiber can be applied inthe form of fiber, fabric, rovings, yarn, thread, or other common fiberapplication forms. The fiber can be applied linearly along the extrudateor can be wrapped at any angle to the extruded linear member in agenerally circular motion.

In the practice of a process for forming the structural members of theinvention, the polymer composite is melted and extruded through aprofile die or orifice to form a rough profile shape. The profile can besolid or hollow. The hollow profile can have a wall thickness of about 1mm to 10 cm or larger if needed. The rough profile shape is thencarefully calibrated in a sizing device which also cools the extrudateto form an extrudate with a carefully defined profile shape. Thethermosetting resin and fiber are then applied to the exterior of thecooled shaped profile and cured to form a reinforcing layer. Thethickness of the reinforcing layer can be about 0.5 mm to about 3 cm orlarger if needed. The resin and fiber can also be passed through acalibration die to shape the resin and fiber prior to and during curingto regulate and fix the exterior dimensions of the structural member. Ina preferred pultrusion method of the invention, a tractor device can beinstalled after the shaping and cooling die to pull the extrudedthermoplastic linear member from the extrusion die through the coolingand sizing device. The pultrusion tractor device can be installed afterthe curing station forming the thermosetting fiber reinforced layer.Preferably, the process is run using a tractor to pull the completedreinforced member from the curing die. This tractor can be sized toprovide all force needed to produce the part.

In certain applications where stress is typically directed onto themember in a specific or defined stress load direction, the fiberreinforcement can be applied only to an area of the profile positionedto support the entire directional load of the stress. Alternatively, theentire surface of the profile can be covered with fiber reinforcement.

Exterior Layer Comprising a Fiber-Reinforced Thermoset

In the structural members of the application, an exterior layer isformed on the thermoplastic core comprising a fiber-reinforcedthermoset. Such an exterior layer is formed using a thermosetting resin.A variety of thermosetting resins are known for use in suchapplications. Such thermosetting resins include unsaturated polyesterresins, phenolic resins, epoxy resins, high-performance epoxy resins,bismaleimides including modified bismaleimides such as epoxymodifications, biscyanate modifications, rubber-toughened bismaleimides,thermoplastic-toughened bismaleimides, and others. In the practice ofthis invention, the preferred resins comprise unsaturated polyesterresins, phenolic resins and epoxy resins.

Polyester resins are manufactured by the reaction of a dibasic acid witha glycol. Dibasic acids used in polyester production are phthalicanhydride, isophthalic acid, maleic acid and adipic acid. The phthalicacid provides stiffness, hardness and temperature resistance; maleicacid provides vinyl saturation to accommodate free radical cure; andadipic acid provides flexibility and ductility to the cured resin.Commonly used glycols are propylene glycol which reduces crystallinetendencies and improves solubility in styrene. Ethylene glycol anddiethylene glycol reduce crystallization tendencies. The diacids andglycols are condensed eliminating water and are then dissolved in avinyl monomer to a suitable viscosity. Vinyl monomers include styrene,vinyltoluene, paramethylstyrene, methylmethacrylate, and diallylphthalate. The addition of a polymerization initiator, such ashydroquinone, tertiary butylcatechol or phenothiazine extends the shelflife of the uncured polyester resin. Resins based on phthalic anhydrideare termed orthophthalic polyesters and resins based on isophthalic acidare termed isophthalic polyesters. The viscosity of the unsaturatedpolyester resin can be tailored to an application. Low viscosity isimportant in the fabrication of fiber-reinforced composites to ensuregood wetting and subsequent high adhesion of the reinforcing layer tothe underlying substrate. Poor wetting can result in large losses ofmechanical properties. Typically, polyesters are manufactured with astyrene concentration or other monomer concentration producing resinhaving an uncured viscosity of 200-1,000 mPa.s(cP). Specialty resins mayhave a viscosity that ranges from about 20 cP to 2,000 cP. Unsaturatedpolyester resins are typically cured by free radical initiators commonlyproduced using peroxide materials. A wide variety of peroxide initiatorsare available and are commonly used. The peroxide initiators thermallydecompose forming free radical initiating species.

Phenolic resins can also be used in the manufacture of the structuralmembers of the invention. Phenolic resins typically comprise aphenol-formaldehyde resin. Such resins are inherently fire resistant,heat resistant and are low in cost. Phenolic resins are typicallyformulated by blending phenol and less than a stoichiometric amount offormaldehyde. These materials are condensed with an acid catalystresulting in a thermoplastic intermediate resin called NOVOLAK. Theseresins are oligomeric species terminated by phenolic groups. In thepresence of a curing agent and optional heat, the oligomeric speciescure to form a very high molecular weight thermoset resin. Curing agentsfor novalaks are typically aldehyde compounds or methylene (--CH₂ --)donors. Aldehydic curing agents include paraformaldehyde,hexamethylenetetraamine, formaldehyde, propionaldehyde, glyoxal andhexamethylmethoxy melamine.

Epoxy resins are also used in forming thermoset-reinforcing layers.Typical epoxy resin systems are based on an oxirane reaction with anactive hydrogen. Epoxy resins are generally characterized as oligomericmaterials that contain one or more epoxy (oxirane) groups per molecule.The value of epoxy resins relates to their ease of processing into avariety of useful products or shapes including coatings, structuralcomponents of a variety of shape and size. Epoxy groups in the resin arecured with an appropriate curing agent, typically an amine. A variety ofcommercially available epoxy resins based on phenol, bisphenol, aromaticdiacids, aromatic polyamines and others are well known. Specificexamples of available commercial resins include a phenolic novolak epoxyresin, glycidated polybasic acid, glycidated polyamine (N, N, N',N'-tetraglycidyl-4,4'-diamino diphenol methane) and glycidated bisphenolA oligomers. Epoxy resins are cured into useful products using curing orcross linking chemical agents. Two principal classes of curing agentsused in epoxy resins for advanced composite materials are aromaticdiamines and acid anhydrides. Such materials include M-phenylenediamine;4,4'-methylene dianiline; 4,4'-diaminodiphenyl sulfone; Nadic MethylAnhydride; hexahydrophthalic anhydride; methyltetrahydrophthalicanhydride and others.

Fiber-reinforcing materials that can be used in the structural membersof the invention typically include high strength fibers such as carbonfibers, glass fibers, aramid fibers, steel fibers, boron fibers, siliconcarbide fibers, polyethylene fibers, polyimide fibers and others. Suchfibers can be used in the form a single filament, a multifilamentthread, a yarn, a roving, a non-woven fabric or a woven fabric material.The fiber, roving, yarn or fabric can be applied linearly along theprofile or wrapped, or otherwise formed on the profile in an appropriatepattern that can be cured to form the reinforcing structure.

Strachan, U.S. Pat. No. 5,120,380, teaches an in-line manufacture offiber filled pultruded profiles. The Strachan technology involvesforming hollow profiles using a long heated mandrel which can be filledwith foam. Strachan uses a driven air blast to maintain a hollow uncuredmember to prevent collapse of the profile and to maintain its shapeduring curing. This process is slow, requires long support mandrelsshaped to the required hollow profile and limits the practicality ofproducing some profiles at economical rates.

The process of the invention uses a continuously extruded and cooledprofile as a mandrel upon which resin and fiber or strips of reinforcedmedia are applied to the mandrel/extrudate. The use of the extrudate asa mandrel substantially increases throughput, provides an accurate gaugeof sizing rapid economical throughput. Further, the process allows forgreater thickness range of the resulting structural member, increasedproduction rates, flexibility in placement of reinforcing materials,thermally or vibrationally weldable profiles, permits the inclusion of"foamed-in-place" areas to facilitate screw, nail or other fastenerretention, has added strength over other reinforced media due to asynergistic bonding between the core and the reinforcing layer. Thecharacteristics of the preferred thermoplastic fiber composite corehighlighted in the improved physical properties including a high heatdistortion temperature (HDT) in excess of 100° C., a Young's modulus orspecific modulus in excess of 500,000 psi preferably greater than1,000,000 psi and an elongation at break of less than 3% and commonlybetween 1 and 3%, a tensile strength of greater than 6,500 psi.

Method

FIG. 1 shows the general method. Pellets of FIBREX™ a PVC/wood fibercomposite of about 60 parts PVC and 40 parts wood fiber are fed into anextruder (1) via the extruder throat (2). The pellets are heated, mixedand compressed in the extruder barrel (3), and then pushed via theextruder screw (4) through an adapter (5) and then a shaped die (6). Onexiting the die, the profile (7) is pulled by a puller (8) through aseries of vacuum sizers (9) or vacuum box (10) with integral sizingplates (11). The vacuum sizers (9) and/or vacuum box (10) spray water(19) onto the profile to reduce its temperature to below the H.D.T. ofFIBREX™. This temperature is not to be construed as critical since thosefamiliar with the art will recognize temperature variations as beingpart of the running process truly relevant to each profile.

From the profile puller (8) the profile (7) is fed through a pultrusiondie (20).

At the same time, continuous strands of fiber (13) are soaked in athermoset resin by being pulled through a wetting bath (21) and thenthrough the pultrusion die (20). This process forms a bond between theFIBREX™ center mandrel and the reinforced thermoset resin.

Those familiar with the art will recognize the possibility ofsubstituting woven cloth for strands should the profile design sorequire it.

Prior to entering the die (20) the resin wetted fibers are subjected toheating by--but not limited to--R. F. waves (12) to facilitate curing.Upon exiting the pultrusion die (20) the profile is fully shaped andcured. Dies (20 & 6) are heated and such heats are controlled to producethe desired profiles and affect the rate of production.

The cured profile is pulled from the pultrusion die by a second puller(17) and then cut to length (18).

FIG. 2 shows a cross-section of a structural member of the invention.The structural member includes a fiber reinforced thermoplastic layer 21covered by a fiber reinforced thermosetting layer 20. The thickness ofthese layers typically ranges from about 0.1 to about 0.3 inches. Thestructural member is in the form of a relatively complex profile shape,generally rectangular, having dimensions of about 1-3 inches×2-4 inches.The core fiber reinforced thermoplastic mandrel shape has a complexstructure 23 which represents a variety of complex shapes that can beintroduced into a load bearing structural member. The fiber reinforcedthermosetting layer 20 is introduced into a channel in the fiberreinforced thermoplastic layer. The material is fully contacted with theinterior of channel 23 without the formation of any substantial bubblesor voids. Such complex shapes can add to both the utility of astructural member in a particular application or can add structuralengineering properties to the overall member.

The structural members of this invention are fiber-thermoset reinforcedpolymer and wood fiber extrusions having a useful cross-sectional shapethat can be adapted to any structural application in construction ofbuildings, cars, airplanes, bridges, utility poles,etc. The members canbe used in window or door construction and the installation of usefulwindow components or parts into the structural member. The structuralmember can be an extrusion in the form or shape of rail, jamb, stile,sill, track, stop or sash. Additionally, non-structural trim elementssuch as grid, cove, quarter-round, etc., can be made. The extruded orinjection molded structural member comprises a hollow cross-sectionhaving a rigid exterior shell or wall, at least one internal structuralor support web and at least one internal structural fastener anchor. Theshell, web and anchor in cooperation have sufficient strength to permitthe structural member to withstand normal wear and tear related to theoperation of the window or door. Fasteners can be used to assemble thewindow or door unit. The fasteners must remain secure during window lifeto survive as a structural member or component of the residential orcommercial architecture. We have further found that the structuralmembers of the invention can be joined by fusing mating surfaces formedin the structural member at elevated temperature to form a welded jointhaving superior strength and rigidity when compared to prior art woodenmembers.

The interior of the structural member is commonly provided with one ormore internal structural webs which in a direction of applied stresssupports the structure. Structural web typically comprises a wall, post,support member, or other formed structural element which increasescompressive strength, torsion strength, or other structural ormechanical property. Such structural web connects the adjacent oropposing surfaces of the interior of the structural member. More thanone structural web can be placed to carry stress from surface to surfaceat the locations of the application of stress to protect the structuralmember from crushing, torsional failure or general breakage. Typically,such support webs are extruded or injection molded during themanufacture of the structural material. However, a support can be postadded from parts made during separate manufacturing operations.

The internal space of the structural member can also contain a fasteneranchor or fastener installation support. Such an anchor or support meansprovides a locus for the introduction of a screw, nail, bolt or otherfastener used in either assembling the unit or anchoring the unit to arough opening in the commercial or residential structure. The anchor webtypically is conformed to adapt itself to the geometry of the anchor andcan simply comprise an angular opening in a formed composite structure,can comprise opposing surfaces having a gap or valley approximatelyequal to the screw thickness, can be geometrically formed to match a keyor other lock mechanism, or can take the form of any commonly availableautomatic fastener means available to the window manufacturer fromfastener or anchor parts manufactured by companies such as AmerockCorp., Illinois Tool Works and others.

The structural member of the invention can have premolded paths or pathsmachined into the molded thermoplastic composite for passage of door orwindow units, fasteners such as screws, nails, etc. Such paths can becounter sunk, metal lined, or otherwise adapted to the geometry or thecomposition of the fastener materials. The structural member can havemating surfaces premolded in order to provide rapid assembly with otherwindow components of similar or different compositions having similarlyadapted mating surfaces. Further, the structural member can have matingsurfaces formed in the shell of the structural member adapted tomoveable window sash or door sash or other moveable parts used in windowoperations.

The structural member of the invention can have a mating surface adaptedfor the attachment of the weigh subfloor or base, framing studs or sidemolding or beam, top portion of the structural member to the roughopening. Such a mating surface can be flat or can have a geometrydesigned to permit easy installation, sufficient support and attachmentto the rough opening. The structural member shell can have othersurfaces adapted to an exterior trim and interior mating with wood trimpieces and other surfaces formed into the exposed sides of thestructural member adapted to the installation of metal runners, woodtrim parts, door runner supports, or other metal, plastic, or woodmembers commonly used in the assembly of windows and doors.

Using extrusion methods a pellet and extruding the pellet into astructural member, an extruded piece as shown in FIG. 2, extrusion 20was manufactured. The wall thickness of any of the elements of theextrudate was about 0.165 inches.

A Cincinnati Millicon extruder with an HP barrel, a Cincinnatipelletizer screws, and AEG K-20 pelletizing head with 260 holes, eachhole having a diameter of about 0.0200 inches was used to make a pellet.The input to the pelletizer comprise approximately 60 wt-% polymer and40 wt-% sawdust. The polymer material comprises a thermoplastic mixtureof approximately 100 parts of vinyl chloride homopolymer, about 15 partstitanium dioxide, about 2 parts ethylene-bis-stearimide wax lubricant,about 1.5 parts calcium stearate, about 7.5 parts Rohm & Haas 980-Tacrylic resin impact modifier/process aid and about 2 parts of dimethyltin thioglycolate. The sawdust input comprises a wood fiber particlecontaining about 5 wt-% recycled polyvinyl chloride having a compositionsubstantially identical to the polyvinyl chloride recited above. Theinitial melt temperature of the extruder was maintained between 375° C.and 425° C. The pelletizer was operated on a vinyl/sawdust combinedratio through put of about 800 pounds/hour. In the initial extruder feedzone, the barrel temperature was maintained between 215°-225° C. In theintake zone, the barrel was maintained at 215°-225° C., and thecompression zone was maintained at between 205°-215° C. and in the meltzone the temperature was maintained at 195°-205° C. The die was dividedinto three zones, the first zone at 185°-195° C., the second zone at185°-195° C. and in the final die zone 195°-205° C. The pelletizing headwas operated at a setting providing 100-300 rpm resulting in a pelletwith a diameter of about 5 mm and a length as shown in the followingTable.

In a similar fashion the core extruded from a vinyl wood compositepellet using an extruder within an appropriate extruder die. The melttemperature of the input to the machine was 390°-420° F. A vacuum waspulled on the melt mass of no less than 3 inches mercury. The melttemperatures through the extruder was maintained at the followingtemperature settings:

    ______________________________________                                        Barrel Zone No. 1                                                                              220-230° C.                                           Barrel Zone No. 2                                                                              220-230° C.                                           Barrel Zone No. 3                                                                              215-225° C.                                           Barrel Zone No. 4                                                                              200-210° C.                                           Barrel Zone No. 5                                                                              185-195° C.                                           Die Zone No. 6   175-185° C.                                           Die Zone No. 7   175-185° C.                                           Die Zone No. 8   175-185° C.                                           ______________________________________                                    

The screw heater oil stream was maintained at 180°-190° C. The materialwas extruded at a line speed maintained between 5 and 7 ft./min.

EXPERIMENTAL

SHOP ORDER: MANUAL LAY UP OF OVERWRAP OF PSII BEAM WITH E-GLASS CLOTHAND ROOM TEMPERATURE CURE POLYESTER RESIN

    ______________________________________                                        MATERIAL QUANTITIES:                                                          DESCRIPTION       QUANTITY                                                    ______________________________________                                        PSII beam section length >15"                                                 (rectangular profile about                                                    2 inches × 4 inches-                                                    0.16 inch thickness)                                                          1522 E-glass plain weave fabric                                                                 19 plies @-15" × 12"                                                    (15" dimension along warp)                                                    3 plies @-16" × 13"                                                     (orient for best nesting)                                   Ashland Aropol 7240 T 15 room                                                                   225 grams                                                   temperature cure polyester                                                    resin                                                                         MEKP-9 catalyst   3 grams                                                     perforated release film                                                                         1 piece @ 16" × 13"                                   non-perforated release film                                                                     1 piece @ 16" × 14"                                   felt breather     1 piece @ 20" × 26"                                   bagging film      1 piece @ 26" × 30"                                   bag sealant tape  ˜56"                                                  sheet metal caul plates                                                                         2 @ 4" × 12"                                                            2 @ 2" × 12"                                          ______________________________________                                    

PREPARATION OF MATERIALS:

1-1. Lightly sand surface of PSII beam section with 180 grit sandpaper.With clean cloth and/or air clean off dust from sanding.

1-2. Cut plies of E-glass cloth and pieces of perforated release film,non-perforated release film, breather, and bagging fin to dimensionsgiven in "MATERIAL QUANTITIES". Cut sheet metal caul plates and removeany burrs or sharp edges.

1-3. Dry fit the E-glass cloth and process materials around the PSIIbeam.

1-4. Cut two holes in the bagging film for two ports, one for the vacuumsource and one for the gauge to measure vacuum pressure. The two vacuumports should be located off of the PSII beam.

1-5. Lay down the bag sealant tape along the permieter of approximatelyone half of the bag. Do not remove the film from the sealant tape.

1-6. Locate the two ports in the vacuum bag.

1-7. Lay down a piece of plastic film on a flat surface wherewetting-out of the plies will occur.

1-8. Weigh out polyester resin in plastic container. Weigh out catalystin a graduated cylinder. Add the catalyst to the resin and mixthoroughly.

LAY-UP PROCESS:

2-1. With PSII beam in holding fixture, brush a coat of resin on thePSII beam.

2-2. On the piece of plastic film brush the resin on one 15"×12" ply ofE-glass cloth.

2-3. Wrap the ply all the way around the PSII beam. Squeegee (from thecenter toward the edges) the cloth to remove any entrapped air.

2-4. Repeat steps 2--2 and 2-3 until all 19 plies are applied to thePSII beam. The overlap or butt joint of each ply should be offset fromthe previous ply approximately 0.5".

VACUUM BAGGING AND CURE:

3-1. Wrap the perforated release film around the PSII/E-glass/polyester(hybrid) beam.

3-2. Wrap the three 16"×13" plies of E-glass cloth (bleeder) around theperforated release film.

3-3. Wrap the non-perforated release film around the bleeder.

3-4. Locate the four caul plates on each of the four faces of the beamand hold in place with tape.

3-5. Wrap the breather around the caul plates.

3-6. Remove the film from the bag sealant tape. Wrap the bagging filmaround the breather and squeeze the bag sealant tape to seal the bag.

3-7. Connect the vacuum source and draw vacuum. Check for leaks invacuum bag and seal.

3-8. Cure at room temperature for 16 hours minimum.

Flexural testing was conducted according to the generic specificationsset forth by ASTM D-790. The span length was 60 inches; loading rate was0.35 in/min. Load versus displacement slopes were measured using anInstron 4505. In this manner, the load versus displacement slope, m, ofthe composite beam was measured to be 1278 lb/in.

Beam theory predicts the load slope, m, to be: ##EQU1## wherein:

E=the beam material flexural modulus, psi

I=moment of inertia of the beam, in⁴

L=beam span length between supports, in

Flexural modulus values of FIBREX™ and the fiberglass reinforcedpolyester (FRP) material prepared, as described, were measured inseparate, independent experiments. These values were found to be 740,000psi and 2,000,000 psi, respectively. The moments of inertia of theFIBREX™ and FRP layers (See FIG. 2) in this example are 1.273 in⁴ and2.073 in⁴, respectively.

If there were no interaction between the two material layers, one wouldexpect the load slope contribution from each to be additive: ##EQU2##

The difference between the predicted load slope (1130 lb/hr) and themeasured load slope (1278 lb/in) demonstrates an interaction between thecomposite layers.

Testing the adhesive bond in shear between the FIBREX™ and thefiberglass reinforced polyester (FRP) was completed according to ASTMD-3163. The crosshead speed used was 0.17 in/min and the bond area was0.25 in². Loads in excess of 450 lbs. were applied to the bond. Thecorresponding minimum shear strength was calculated as follows:

    t=P/A

where

P=max load (lb)

A=bond area (in²) ##EQU3##

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

We claim:
 1. A composite structural member having a core and anintimately bonded exterior layer, said member comprising:(a) athermoplastic linear extruded core comprising a polymer compositecomposition comprising a fiber reinforced polyvinyl chloride; and (b) anexterior layer comprising a fiber-reinforced thermoset; wherein the coreis a noncircular profile shape.
 2. The member of claim 1 wherein thecore comprises a linear extrudate having a hollow square cross sectionwith a wall thickness greater than 1 mm.
 3. The member of claim 1wherein the core comprises a linear extrudate having a hollowrectangular cross section with a wall thickness greater than 1 mm. 4.The member of claim 1 wherein the exterior layer covers the entiresurface of the linear core.
 5. The member of claim 1 wherein theexterior layer is placed on the core to provide reinforcement in adefined direction of applied stress.
 6. The member of claim 1 whereinthe core comprises an extruded thermoplastic composite comprising aminor proportion of polyvinyl chloride and a major proportion of areinforcing cellulosic fiber.
 7. The member of claim 6 wherein thethermoplastic polymer is present at a concentration of about 15 to 40wt-% of the core.
 8. The composite of claim 6 wherein the cellulosicfiber in a wood fiber with a particle size of about 0.3 mm to 10 mm andan aspect ratio of about 1 to
 10. 9. The composite of claim 6 whereinthe cellulosic fiber is a wood fiber with a length of about 0.3 mm to 3mm and a width of 0.1 mm to 3 mm and an aspect ratio of about 2 to 7.10. The member of claim 1 wherein the thermoset comprises an unsaturatedpolyester resin.
 11. The member of claim 1 wherein the fiber of theexterior layer comprises glass fiber.
 12. The member of claim 11 whereinthere is about 20 to 40 wt-% of thermoset resin and about 80 to 60 wt-%of glass fiber in the exterior layer.